Coated tool

ABSTRACT

The coated tool has a substrate and a coating layer. The coating layer contains alternating first and second laminated structures. The first laminated structure contains at least two kinds of alternating layers having different compositions. An average thickness of the layers contained in the first laminated structure is 60 nm or more and 500 nm or less. The second laminated structure contains at least two kinds of alternating layers having different compositions. An average thickness of the layers contained in the second laminated structure is 2 nm or more and less than 60 nm. The layers contained in the first laminated structure and the second laminated structure contain a compound having one or more specific metals and at least one or more of carbon, nitrogen, oxygen and boron. Average thickness(es) of the first and second laminated structure is/are continuously or stepwisely increased in a direction away from the substrate.

RELATED APPLICATIONS

This is a 371 US National Phase of International Patent Application No. PCT/JP2015/061195 filed Apr. 10, 2015 and published as WO 2015/156383A1 on Oct. 15, 2015, which claims priority to JP 2014-080936, filed Apr. 10, 2014. The contents of the aforementioned applications are incorporated by reference in their entirety.

TECHNICAL FIELD

The present invention relates to a coated tool.

BACKGROUND ART

In recent years, cutting with high efficiency has been highly demanded. Accompanying with heightening of this demand, a cutting tool having a longer tool life than that of the conventional ones has been required. Thus, as characteristics required for the tool materials, it is important to improve characteristics relating to lifetime of a cutting tool. For example, it is more important to improve wear resistance and fracture resistance of the cutting tool. To improve these characteristics, a coated tool wherein alternately laminated films in which coating films are alternately laminated are formed on a substrate has been used.

To improve characteristics of such alternately laminated films, various techniques have been proposed. In Patent document 1, for example, a cutting tool in which a first layer and a second layer are alternately laminated on a substrate so that these layers become 4 layers or more has been proposed. The first layer contains a complex nitride represented by the compositional formula of (Ti_(1-X)Al_(X))N (X: 0.30 to 0.70 in an atomic ratio). The second layer contains an aluminum oxide phase and a titanium nitride phase. A ratio of the aluminum oxide phase in the second layer is 35 to 65% by mass based on the total of the aluminum oxide phase and the titanium nitride phase. Average thicknesses of the first layer and the second layer are each 0.2 to 1 μm. An average thickness of the first layer and the second layer in total is 2 to 10 μm. It has been disclosed that the cutting tool shows excellent wear resistance even under the heavy cutting conditions.

In Patent document 2, a cutting tool in which a specific metal element or a compound thereof, and a specific alloy compound are laminated onto a surface of a base material with laminating cycles of 0.4 nm to 50 nm has been proposed. It has been disclosed that the cutting tool has excellent wear resistance.

In Patent document 3, a coated tool containing a first laminated structure and a second laminated structure has been proposed. The first laminated structure has a structure in which two or more layers having different compositions are periodically laminated. The average thickness of the respective layers contained in the first laminated structure is 60 nm or more and 500 nm or less. The second laminated structure has a structure in which two or more layers having different compositions are periodically laminated. The average thickness of the respective layers contained in the second laminated structure is 2 nm or more and less than 60 nm.

PRIOR ART DOCUMENT Patent Document

Patent document 1: JP 2003-200306A

Patent document 2: JP Hei.7-205361A

Patent document 3: WO 2014/025057A

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

In recent years, high speed, high feeding and deep cutting in a cutting process becomes more remarkable. Thus, fracture of the tool has been frequently generated. For example, due to the load applied to the cutting edge during the processing, cracks are generated at the surface of the tool. By propagating the cracks to the substrate, fracture of the tool is generated. In addition, if a temperature of the cutting edge is rapidly raised or lowered, cracks are generated at the substrate. By propagating the cracks to the coating layer, fracture of the tool is generated.

According to such a background, the cutting tool disclosed in the above-mentioned Patent document 1 has a problem that wear resistance is poor since hardness of the film is insufficient. Also, the cutting tool disclosed in Patent document 2 has high wear resistance, but has a problem that facture of the tool is likely generated. The cutting tool disclosed in Patent document 3 cannot fulfil the required properties since wear resistance is insufficient.

The present invention has been done to solve these problems. An object of the present invention is to suppress wear due to dropping of particles at the coating layer without lowering fracture resistance in a coated tool which can be used for severe cutting. In addition, an object of the present invention is to provide a coated tool which can be used for cutting for a long period of time.

Means to Solve the Problems

The present inventors have intensively researched on elongation of tool life of a coated tool. The present inventors have accomplished improvement in wear resistance without lowering fracture resistance of the coated tool by improving a constitution of the coating layer. As a result, tool life of the coated tool could be elongated.

That is, the summary of the present invention is as follows.

-   (1) A coated tool which comprises a substrate, and

a coating layer formed onto a surface of the substrate,

wherein the coating layer contains a first laminated structure and a second laminated structure,

the first laminated structure and the second laminated structure are laminated alternately and continuously twice or more,

the first laminated structure contains at least two kinds of layers having different compositions, and the two kinds of the layers are alternately laminated twice or more,

an average layer thickness of the layers contained in the first laminated structure is 60 nm or more and 500 nm or less,

the second laminated structure contains at least two kinds of layers having different compositions, and the two kinds of the layers are alternately laminated twice or more,

an average layer thickness of the layers contained in the second laminated structure is 2 nm or more and less than 60 nm,

the layers contained in the first laminated structure and the second laminated structure contain a compound which contains at least one metal element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Al, Si, Sr, Y, Sn and Bi, and at least one non-metal element selected from the group consisting of carbon, nitrogen, oxygen and boron,

an average thickness(es) of the first laminated structure and/or the second laminated structure is/are continuously or stepwisely increased from the substrate side toward a surface side of the coating layer.

-   (2) The coated tool according to (1), wherein an average thickness     of the first laminated structure is 0.2 μm or more and 6 μm or less. -   (3) The coated tool according to (1) or (2), wherein an average     thickness of the second laminated structure is 0.02 μm or more and 6     μm or less. -   (4) The coated tool according to any one of (1) to (3), wherein an     average thickness of the whole coating layer is 0.22 μm or more and     12 μm or less. -   (5) The coated tool according to any one of (1) to (4), wherein when     an average thickness of the first laminated structure nearest to the     substrate is made TA1, and an average thickness of the first     laminated structure nearest to the surface of the coating layer is     made TB1, then a ratio of TA1 to TB1 is 5% or more and 50% or less. -   (6) The coated tool according to any one of (1) to (5), wherein when     an average thickness of the second laminated structure nearest to     the substrate is made TA2, and an average thickness of the second     laminated structure nearest to the surface of the coating layer is     made TB2, then a ratio of TA2 to TB2 is 5% or more and 50% or less. -   (7) The coated tool according to any one of (1) to (6), wherein when     an average thickness of the layers contained in the first laminated     structure nearest to the substrate is made TC1, and an average     thickness of the layers contained in the first laminated structure     nearest to the surface of the coating layer is made TD1, then a     ratio of TC1 to TD1 is 12% or more and 70% or less. -   (8) The coated tool according to any one of (1) to (7), wherein when     an average thickness of the layers contained in the second laminated     structure nearest to the substrate is made TC2, and an average     thickness of the layers contained in the second laminated structure     nearest to the surface of the coating layer is made TD2, then a     ratio of TC2 to TD2 is 5% or more and 70% or less. -   (9) The coated tool according to any one of (1) to (8), wherein the     layers contained in the first laminated structure and the layers     contained in the second laminated structure contain a compound     comprising at least two metal elements selected from the group     consisting of Ti, Nb, Ta, Cr, W, Al, Si, Sr and Y, and at least one     non-metal element selected from the group consisting of carbon,     nitrogen, oxygen and boron.

Effects of the Invention

The coated tool of the present invention is excellent in wear resistance and fracture resistance, so that it can accomplish the effect that tool life can be elongated than those of the conventional ones.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is an example of a schematic drawing of a cross-sectional structure of the coated tool of the present invention.

EMBODIMENT TO CARRY OUT THE INVENTION

The coated tool of the present invention comprises a substrate and a coating layer formed onto a surface of the substrate. The substrate of the present invention may be any material so long as it is used as a substrate of the coated tool. The substrate of the present invention is not particularly limited and may be, for example, a cemented carbide, cermet, ceramics, a cubic boron nitride sintered body, a diamond sintered body and high-speed steel. Among these materials, a cemented carbide is preferred. This is because the cemented carbide is excellent in wear resistance and fracture resistance.

In the coated tool of the present invention, an average thickness of the whole coating layer is preferably 0.22 to 12 μm. If the average thickness of the coating layer is less than 0.22 μm, wear resistance of the coated tool tends to be lowered. If the average thickness of the coating layer exceeds 12 μm, fracture resistance of the coated tool tends to be lowered. The average thickness of the whole coating layer is further preferably 1.0 to 8.0 μm.

In the coated tool of the present invention, the coating layer contains a specific first laminated structure and second laminated structure. The respective layers contained in the first laminated structure and the second laminated structure contain a compound comprising at least one metal element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Al, Si, Sr, Y, Sn and Bi, and at least one non-metal element selected from the group consisting of carbon, nitrogen, oxygen and boron. The coated tool of the present invention is excellent in wear resistance.

The layers contained in the first laminated structure and the second laminated structure more preferably contain a compound comprising at least two kinds of metal elements selected from the group consisting of Ti, Nb, Ta, Cr, W, Al, Si, Sr and Y, and at least one non-metal element selected from the group consisting of carbon, nitrogen, oxygen and boron. This is because such a compound has a property of being hard. The compound contained in the layer constituting the first laminated structure may be specifically (Al_(0.50)Ti_(0.50))N, (Al_(0.60)Ti_(0.40))N (Al_(0.67)Ti_(0.33))N, (Al_(0.67)Ti_(0.33))CN, (Al_(0.45)Ti_(0.45)Si_(0.10))N, (Al_(0.45)Ti_(0.45)Y_(0.10))N, (Al_(0.50)Ti_(0.30)Cr_(0.20))N, (Al_(0.50)Ti_(0.45)Nb_(0.05))N, (Al_(0.50)Ti_(0.45)Ta_(0.05))N, (Al_(0.50)Ti_(0.45)W_(0.05))N, (Ti_(0.90)Si_(0.10))N, (Al_(0.50)Cr_(0.50))N, etc.

The metal element(s) contained in the layer constituting the first laminated structure is/are preferably the same as the metal element(s) contained in the other layers constituting the first laminated structure. That is, a plurality of the layers constituting the first laminated structure are preferably constituted by the same kinds of the metal elements. In addition, it is preferred that an absolute value of the difference between a ratio of the specific metal elements contained in the layers constituting the first laminated structure and a ratio of the specific metal elements contained in the other layers constituting the first laminated structure adjacent to the above layer is 5 atomic % or more. “A ratio of the specific metal elements” herein mentioned means a ratio (atomic %) of the number of the atoms of the specific metal elements contained in the layer based on the number of atoms of the whole metal elements contained in the layer.

If the first laminated structure employs such a constitution, crystal lattice becomes inconsistent at the boundary surface between the layers without lowering adhesiveness between a layer constituting the first laminated structure and a layer adjacent to the layer. Therefore, cracks are likely propagated to the direction parallel to the boundary surface of the layers constituting the first laminated structure, whereby propagation of the cracks to the substrate can be effectively suppressed.

With regard to the above-mentioned “absolute value of the difference between a ratio of the specific metal elements contained in a layer and a ratio of the specific metal elements contained in the other layers adjacent to the above layer is 5 atomic % or more”, it is explained in more detail.

For example, when the first laminated structure is constituted by an (Al_(0.55)Ti_(0.45))N layer and an (Al_(0.67)Ti_(0.33))N layer, the kinds of the metal elements contained in the two layers are the same. This is because the two layers both contain Al and Ti. In this case, the number of the atoms of Al contained in the (Al_(0.55)Ti_(0.45))N layer is 55 atomic % based on the number of the atoms of the whole metal elements. The number of the atoms of Al contained in the (Al_(0.67)Ti_(0.33))N layer is 67 atomic % based on the number of the atoms of the whole metal elements. The difference in the ratios of the numbers of the atoms of Al in these two layers is 12 atomic %. Accordingly, in this case, the above-mentioned condition that “the absolute value of the difference is 5 atomic % or more” is satisfied.

For example, when the first laminated structure is constituted by a (Al_(0.49)Ti_(0.39)Cr_(0.12))N layer and a (Al_(0.56)Ti_(0.36)Cr_(0.08))N layer, the kinds of the metal elements contained in the two layers are the same. This is because the two layers both contain Al, Ti and Cr. In this case, the difference in the ratios of the numbers of the atoms of Ti contained in the two layers is 3 atomic %. The difference in the ratios of the numbers of the atoms of Cr contained in the two layers is 4 atomic %. These values are each less than 5 atomic %. However, even in this case, the difference in the ratios of the numbers of the atoms of Al contained in the two layers is 7 atomic %, so that the above-mentioned condition that “an absolute value of the difference is 5 atomic % or more” is satisfied.

In the present specification, when the nitride is shown as (M_(a)L_(b))N, it means that an atomic ratio of the M element based on the whole metal elements is a, and an atomic ratio of the L element based on the whole metal elements is b. For example, (Al_(0.55)Ti_(0.45))N means that an atomic ratio of the Al element based on the whole metal elements is 0.55, and an atomic ratio of the Ti element based on the whole metal elements is 0.45. That is, (Al_(0.55)Ti_(0.45))N shows that an amount of the Al element based on the whole metal element is 55 atomic %, and an amount of the Ti element based on the whole metal element is 45 atomic %.

The metal element(s) contained in the layers constituting the second laminated structure is/are preferably the same as the metal element(s) contained in the other layers constituting the second laminated structure. That is, a plurality of the layers constituting the second laminated structure are preferably constituted by the same kinds of the metal elements. In addition, it is preferred that an absolute value of the difference between a ratio of the specific metal elements contained in a layer constituting the second laminated structure and a ratio of the specific metal elements contained in the other layer constituting the second laminated structure adjacent to the above layer is 5 atomic % or more. “A ratio of the specific metal elements” herein mentioned means a ratio (atomic %) of the number of the atoms of the specific metal elements contained in the layer based on the number of atoms of the whole metal elements contained in the layer.

If the second laminated structure employs such a constitution, crystal lattice becomes inconsistent at the boundary surface between the layers without lowering adhesiveness between a layer constituting the second laminated structure and a layer adjacent to the layer. Therefore, cracks are likely propagated to the direction parallel to the boundary surface of the layers constituting the second laminated structure, whereby propagation of the cracks to the substrate can be effectively suppressed. The meaning of the above-mentioned “absolute value of the difference between a ratio of the specific metal elements contained in a layer and a ratio of the specific metal elements contained in the other layers adjacent to the above layer is 5 atomic % or more” is the same as those explained in the above first laminated structure.

As the other embodiments of the coated tool of the present invention, it is preferred that one or more kinds of the metal elements contained in a layer constituting the first laminated structure is different from the metal elements contained in the other layer constituting the first laminated structure adjacent to the above layer. If one or more kinds of the metal elements is/are different, crystal lattice becomes inconsistent at the boundary surface between the layers, and cracks are likely propagated to the direction parallel to the boundary surface of the layers, whereby propagation of the cracks to the substrate can be effectively suppressed.

For example, when the first laminated structure is constituted by an (Al_(0.50)Ti_(0.50))N layer and an (Al_(0.50)Ti_(0.30)Cr_(0.20))N layer, and the metal elements contained in the two layers are compared to each other, the above condition is satisfied. This is because the two layers contain Al and Ti, but Cr is contained in one layer alone.

For example, when the first laminated structure is constituted by an (Al_(0.50)Cr_(0.50))N layer and an (Al_(0.67)Ti_(0.33))N layer, and the metal elements contained in the two layers are compared to each other, the above condition is satisfied. This is because the two layers contain Al, but Cr and Ti are respectively contained in one layer alone.

Similarly, in the coated tool of the present invention, it is preferred that one or more kinds of the metal elements contained in a layer constituting the second laminated structure is different from the metal elements contained in the other layer constituting the second laminated structure adjacent to the above layer. If one or more kinds of the metal elements is/are different, crystal lattice becomes inconsistent at the boundary surface between the layers, and cracks are likely propagated to the direction parallel to the boundary surface of the layers, whereby propagation of the cracks to the substrate can be effectively suppressed.

The coated tool of the present invention contains a coating layer. The coating layer contains a first laminated structure. The first laminated structure contains two or more layers comprising the above-mentioned compound. The average thickness of the respective layers contained in the first laminated structure is 60 nm or more and 500 nm or less. Two or more layers contained in the first laminated structure are periodically laminated. The periodically laminated structure contains at least two kinds of layers having different compositions. These two kinds of layers are laminated alternately twice or more. When two kinds of layers having different compositions are laminated alternately twice or more, propagation of the cracks is suppressed, so that fracture resistance of the coated tool is further improved.

In the present invention, the minimum unit of the thickness in which lamination of the layers is repeated is called as “laminating cycle”.

FIG. 1 is an example of a schematic drawing of a cross-sectional structure of the coated tool of the present invention. In the following, the laminating cycle is explained by referring to FIG. 1.

For example, Layer A1, Layer B1, Layer C1 and Layer D1 which have different compositions are repeatedly laminated from the substrate (1) toward the surface of the coating layer (2). More specifically, these layers are laminated in the order of Layer A1→Layer B1→Layer C1→Layer D1→Layer A1→Layer B1→Layer C1→Layer D1→ . . . . In this case, the total thickness from Layer A1 to Layer D1 is a “laminating cycle”.

For example, Layer A1 and Layer B1 which have different compositions are repeatedly laminated from the substrate (1) toward the surface of the coating layer (2). More specifically, these layers are laminated in the order of Layer A1→Layer B1→Layer A1→Layer B1→Layer A1→Layer B1→ . . . . In this case, the total of the thickness of Layer A1 and the thickness of Layer B1 is a “laminating cycle”.

To form the first laminated structure, at least two kinds of layers having different compositions are periodically laminated. The average thickness of the respective layers is 60 nm or more and 500 nm or less. By being formed the first laminated structure as mentioned above, the following effects can be obtained.

Cracks generated at the surface of the coating layer during the use of the coated tool reach to the first laminated structure. The cracks reached to the first laminated structure propagate to the direction parallel to the boundary surface of the layers having different compositions. This brings an effect that the propagation of the cracks to the substrate can be prevented. Such an effect can be more heightened by alternately laminating two layers having different compositions twice or more. More specifically, it is preferred that Layer A1 and Layer B1 having different compositions are alternately laminated twice or more from the substrate toward the surface of the coating layer. That is, the first laminated structure preferably contains an alternately laminated structure of Layer A1→Layer B1→Layer A1→Layer B→ . . . .

If the average thickness of the respective layers contained in the first laminated structure is less than 60 nm, propagation of the cracks to the substrate cannot sufficiently be prevented. On the other hand, if the average thickness of the respective layers exceeds 500 nm, fracture resistance of the coated tool is lowered. Therefore, the average thickness of the respective layers contained in the first laminated structure is 60 nm or more and 500 nm or less. The average thickness of the respective layers contained in the first laminated structure is preferably 60 nm or more and 250 nm or less.

If the average thickness of the first laminated structure is less than 0.2 μm, a number (a number of repeated times) of periodically laminating the layers having different compositions becomes small. In this case, the effect of suppressing propagation of cracks to the substrate is lowered. On the other hand, if the average thickness of the first laminated structure exceeds 6 μm, residual compressive stress of the whole coating layer becomes high. As a result, peeling or fracture of the coating layer likely occurs, whereby fracture resistance of the coated tool is lowered. Accordingly, the average thickness of the first laminated structure is preferably 0.2 to 6 μm.

The coated tool of the present invention contains a coating layer. The coating layer contains a second laminated structure. The second laminated structure contains two or more layers comprising the above-mentioned compound. The average thickness of the respective layers contained in the second laminated structure is 2 nm or more and less than 60 nm. Two or more layers contained in the second laminated structure are periodically laminated. The periodically laminated structure contains at least two kinds of layers having different compositions. These two kinds of layers are laminated alternately twice or more. When two kinds of layers having different compositions are laminated alternately twice or more, hardness of the second laminated structure is high, so that wear resistance of the coated tool is further improved.

In the second laminated structure, the minimum unit of the thickness in which lamination of the layers is repeated is called as “laminating cycle”.

For example, in FIG. 1, Layer A2, Layer B2, Layer C2 and Layer D2 which have different compositions are repeatedly laminated from the substrate (1) toward the surface of the coating layer (2). More specifically, these layers are laminated in the order of Layer A2→Layer B2→Layer C2→Layer D2→Layer A2→Layer B2→Layer C2→Layer D2→ . . . . In this case, the total thickness from Layer A2 to Layer D2 is a “laminating cycle”.

For example, Layer A2 and Layer B2 which have different compositions are repeatedly laminated from the substrate (1) toward the surface of the coating layer (2). More specifically, these layers are laminated in the order of Layer A2→Layer B2→Layer A2→Layer 2→Layer A2→Layer B2→ . . . . In this case, total of the thickness of Layer A2 and the thickness of Layer B2 is a “laminating cycle”.

To form the second laminated structure, at least two kinds of layers having different compositions are periodically laminated. The average thickness of the respective layers is 2 nm or more and less than 60 nm. By the second laminated structure being thus formed, hardness of the second laminated structure becomes high whereby wear resistance of the coated tool improves. Such an effect can be more heightened by alternately laminating two layers having different compositions twice or more. More specifically, it is preferred to contain an alternately laminated structure of Layer A2 and Layer B2 having different compositions from the substrate toward the surface of the coating layer like Layer A2→Layer B2→Layer A2→Layer B2→ . . . .

If the average thickness of the respective layers contained in the second laminated structure is less than 2 nm, it is difficult to form a layer having a uniform thickness. If the average thickness of the respective layers contained in the second laminated structure is 60 nm or more, hardness of the second laminated structure is lowered, so that wear resistance of the coated tool is lowered. Further, in this case, difference between the thickness of the second laminated structure and the thickness of the first laminated structure becomes small. As a result, cracks to the direction parallel to the boundary surface of the first laminated structure and the second laminated structure do not propagate, whereby propagation of the cracks to the substrate cannot sufficiently be suppressed. Therefore, the average thickness of the respective layers contained in the second laminated structure is 2 nm or more and less than 60 nm. The average thickness of the respective layers contained in the second laminated structure is further preferably 5 nm or more and 30 nm or less.

If the average thickness of the second laminated structure is less than 0.02 μm, a number (a number of repeated times) of periodically laminating the layers having different compositions becomes small. In this case, the effect of improving hardness of the second laminated structure cannot be obtained. On the other hand, if the average thickness of the second laminated structure exceeds 6 μm, residual compressive stress of the second laminated structure becomes high. As a result, peeling or fracture of the coating layer likely occurs, whereby fracture resistance of the coated tool is lowered. Accordingly, the average thickness of the second laminated structure is preferably 0.02 to 6 μm.

The coated tool of the present invention contains a coating layer. The coating layer contains the first laminated structure excellent in fracture resistance and the second laminated structure excellent in wear resistance. Accordingly, the coated tool of the present invention is excellent in fracture resistance and wear resistance. The coating layer may contain an upper layer. The upper layer is a layer positioned at the surface side of the coating layer than the first laminated structure and the second laminated structure. The surface side of the coating layer means a side of the coating layer positioned opposite to the substrate. In addition, the coating layer may contain a lower layer. The lower layer is a layer positioned at the substrate side than the first laminated structure and the second laminated structure.

Constitutions of the upper layer and the lower layer are not particularly limited. The upper layer and the lower layer preferably contain at least one metal element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Al, Si, Sr, Y, Sn and Bi. Further, the upper layer and the lower layer preferably contain a compound comprising at least one kind of a metal element selected from these metal elements and at least one non-metal element selected from the group consisting of carbon, nitrogen, oxygen and boron. Constitutions of the upper layer and the lower layer are preferably a monolayer or a non-periodical multi-layer. When the upper layer and the lower layer have such a constitution, wear resistance of the upper layer and the lower layer is improved.

The first laminated structure and the second laminated structure are laminated two or more alternately and continuously. If the first laminated structure and the second laminated structure are alternately laminated, cracks are likely propagated to the direction parallel to the boundary surface of the first laminated structure and the second laminated structure. As a result, propagation of the cracks to the substrate can be suppressed, whereby fracture resistance of the coated tool is improved.

Positional relationship of the first laminated structure and the second laminated structure is not particularly limited. The positional relationship of the first laminated structure and the second laminated structure are, for example, any of the following (1) to (4).

-   (1) The first laminated structure is nearest to the substrate, and     the second laminated structure is nearest to the surface of the     coating layer. -   (2) The second laminated structure is nearest to the substrate, and     the first laminated structure is nearest to the surface of the     coating layer. -   (3) The first laminated structure is nearest to the substrate, and     is nearest to the surface of the coating layer. -   (4) The second laminated structure is nearest to the substrate, and     is nearest to the surface of the coating layer.

In the above-mentioned (1) to (4), “the surface of the coating layer” means a surface of the coating layer positioned opposite to the substrate.

Among the above-mentioned positional relationship, (1) is preferred. When the positional relationship of the first laminated structure and the second laminated structure is the above-mentioned (1), residual compressive stress of the first laminated structure is lower than residual compressive stress of the second laminated structure, so that peeling resistance of the coating layer tends to be improved.

The average thickness of the first laminated structure and/or the second laminated structure is continuously or stepwisely increased from the substrate side toward the surface side of the coating layer. This is because wear resistance can be improved without lowering fracture resistance of the coating layer.

At the surface side of the coating layer, the average thickness(es) of the first laminated structure and/or the second laminated structure is/are increased, so that a distance between boundary surfaces of the first laminated structures and the second laminated structures becomes long. When the distance between boundary surfaces of the first laminated structure and the second laminated structure becomes long, the grain size of the first laminated structure at the surface side of the coating layer becomes large. As a result, wear resistance of the coating layer is improved. In addition, the distance between boundary surfaces of the first laminated structure and the second laminated structure becomes long, so that the second laminated structure at the surface side of the coating layer becomes thick. As a result, wear resistance of the coating layer is improved. Therefore, if the average thickness of either of the first laminated structure or the second laminated structure is made thick, wear resistance is improved. If both of the average thicknesses of the first laminated structure and the second laminated structure are made thick, wear resistance is further improved.

In the present invention, “continuously increased” means, for example, that the thickness(es) of the first laminated structure and/or the second laminated structure is/are increased from the substrate side toward the surface side with a certain regularity such as a proportional relationship. However, “continuously increased” is not limited only to the case where the thickness(es) of the first laminated structure and/or the second laminated structure is/are increased in accordance with the proportional relationship. For example, it includes the case where it is increased in accordance with the relation of exponential relationship. In addition, “continuously increased” also includes the case where the thickness tends to be increased from the substrate side toward the surface side. This is because, even in this case, the effect of the present invention can be obtained. For example, the case where a part of the thickness of the coating layer is slightly decreased from the substrate side toward the surface side is also included in the scope of the right of the present invention.

In the present invention, “stepwisely increased” means, for example, that the thickness(es) of the first laminated structure and/or the second laminated structure is/are increased irregularly from the substrate side toward the surface side. For example, “stepwisely increased” includes the case where the thickness of the first laminated structure and/or the second laminated structure at the outermost surface alone is/are increased. In addition, “stepwisely increased” also includes the case where the thickness tends to be increased from the substrate side toward the surface side. This is because, even in this case, the effect of the present invention can be obtained. For example, the case where a part of the thickness of the coating layer is slightly decreased from the substrate side toward the surface side is also included in the scope of the right of the present invention.

When the average thickness of the first laminated structure nearest to the substrate is made TA1, and the average thickness of the first laminated structure nearest to the surface of the coating layer is made TB1, then a ratio of TA1 to TB1 ((TA1/TB1)×100) is preferably 5% or more and 50% or less, more preferably 5% or more and 30% or less. If the ratio of TA1 to TB1 is less than 5%, the distance of the boundary surfaces of the first laminated structure and the second laminated structure becomes long. As a result, the effect of suppressing propagation of the cracks to the substrate may be lowered. On the other hand, if the ratio of TA1 to TB1 exceeds 50%, the effect of coarsening the grain size of the first laminated structure becomes a little. As a result, wear resistance of the coated tool may be lowered.

When the average thickness of the second laminated structure nearest to the substrate is made TA2, and the average thickness of the second laminated structure nearest to the surface of the coating layer is made TB2, then a ratio of TA2 to TB2 ((TA2/TB2)×100) is preferably 5% or more and 50% or less, more preferably 5% or more and 30% or less. If the ratio of TA2 to TB2 is less than 5%, the distance of the boundary surfaces of the first laminated structure and the second laminated structure becomes long. As a result, the effect of suppressing propagation of the cracks to the substrate may be lowered. On the other hand, if the ratio of TA2 to TB2 exceeds 50%, the effect obtained by making the second laminated structure thick film as compared to that of the first laminated structure cannot be obtained. As a result, wear resistance of the coated tool may be lowered.

The average thickness of the respective layers constituting the first laminated structure and the second laminated structure is preferably increased continuously or stepwisely from the substrate side toward the surface side of the coating layer. This is because lowering in fracture resistance of the coated tool can be suppressed, whereby wear resistance is improved.

In the present invention, “continuously increased” means, for example, that the average thickness of the respective layers constituting the first laminated structure and/or the second laminated structure are increased from the substrate side toward the surface side with a certain regularity such as a proportional relationship. However, “continuously increased” is not limited only to the case where the average thickness of the respective layers constituting the first laminated structure and/or the second laminated structure is increased in accordance with the proportional relationship. For example, “continuously increased” includes the case where the thicknesses of the respective layers are increased in accordance with the relation of exponential relationship. In addition, “continuously increased” also includes the case where the thickness tends to be increased from the substrate side toward the surface side. This is because, even in this case, the effect of the present invention can be obtained. For example, the case where a part of the thickness of the coating layer is slightly decreased from the substrate side toward the surface side is also included in the scope of the right of the present invention.

In the present invention, “stepwisely increased” means, for example, that the thicknesses of the respective layers constituting the first laminated structure and/or the second laminated structure are increased irregularly from the substrate side toward the surface side. For example, “stepwisely increased” includes the case where the thicknesses of the respective layers constituting the first laminated structure and/or the second laminated structure at the outermost surface alone are increased. In addition, “stepwisely increased” also includes the case where the thickness tends to be increased from the substrate side toward the surface side. This is because, even in this case, the effect of the present invention can be obtained. For example, the case where a part of the thickness of the coating layer is slightly decreased from the substrate side toward the surface side is also included in the scope of the right of the present invention.

When the average thickness of the layers contained in the first laminated structure nearest to the substrate is made TC1, and the average thickness of the layers contained in the first laminated structure nearest to the surface of the coating layer is made TD1, then a ratio of TC1 to TD1 ((TC1/TD1)×100) is preferably 12% or more and 70% or less, more preferably 30% or more and 60% or less. If the ratio of TC1 to TD1 is less than 12%, the effect of suppressing propagation of the cracks to the substrate is lowered. As a result, fracture resistance may be lowered. On the other hand, if the ratio of TC1 to TD1 exceeds 70%, the effect of coarsening the grain size of the first laminated structure becomes a little. As a result, wear resistance may be lowered.

Incidentally, “the average thickness of the layers contained in the first laminated structure” is a value obtained as follows.

For example, when Layer A1 and Layer B1 are laminated in this order repeating 100 times as Layer A1→Layer B1→Layer A1→Layer B1→Layer A1→Layer B1→ . . . , the sum of the laminating cycles repeated 100 times is obtained. Next, a value in which the sum of the laminating cycles is divided by 100 which is a number of the times repeated is obtained. This value is “the average thickness of the layers contained in the first laminated structure”. That is, when the first laminated structure comprises “Layer A1→Layer B1→Layer A1→Layer B1→Layer A1→Layer B→ . . . ”, the average thickness of “Layer A1→Layer B1→” is “the average thickness of the layers contained in the first laminated structure”.

When the average thickness of the layers contained in the second laminated structure nearest to the substrate is made TC2, and the average thickness of the layers contained in the second laminated structure nearest to the surface of the coating layer is made TD2, then a ratio of TC2 to TD2 ((TC2/TD2)×100) is preferably 5% or more and 70% or less, more preferably 30% or more and 60% or less. If the ratio of TC2 to TD2 is less than 5%, the effect of suppressing propagation of the cracks to the substrate is lowered. As a result, fracture resistance may be lowered. On the other hand, if the ratio of TC2 to TD2 exceeds 70%, wear resistance at the surface side of the coating layer tends to be lowered. Incidentally, “the average thickness of the layers contained in the second laminated structure” is a value obtained as follows.

For example, when Layer A2 and Layer B2 are laminated in this order repeating 100 times as Layer A2→Layer B2→Layer A2→Layer B2→Layer A2→Layer B2→ . . . , the sum of the laminating cycles repeated 100 times is obtained. Next, a value in which the sum of the laminating cycles is divided by 100 which is a number of the times repeated is obtained. This value is “the average thickness of the layers contained in the second laminated structure”. That is, when the second laminated structure comprises “Layer A2→Layer B2→Layer A2→Layer B2→Layer A2→Layer B2→ . . . ”, the average thickness of “Layer A2→Layer B2” is “the average thickness of the layers contained in the second laminated structure”.

A process for preparing the coating layer in the coated tool of the present invention is not particularly limited. For example, the coating layer can be prepared by the physical vapor deposition method such as the ion plating method, the arc ion plating method, the sputtering method and the ion mixing method, etc. For example, the first laminated structure and the second laminated structure explained above can be formed on the substrate by the physical vapor deposition method. In particular, the coating layer formed by the arc ion plating method has high adhesiveness to the substrate. Accordingly, among these methods, the arc ion plating method is preferred.

The respective layers can be formed onto the surface of the substrate by the conventional coating method. According to the above, the coated tool of the present invention can be prepared. The process for preparing the coated tool of the present invention is, for example, as follows.

A substrate processed to a tool shape is charged in a reaction vessel of a physical vapor deposition device. Next, inside the reaction vessel is evacuated until a pressure becomes 1×10⁻² Pa or lower. After evacuation, the substrate is heated to 200 to 800° C. by a heater in the reaction vessel. After heating, an Ar gas is introduced into the reaction vessel, and the pressure is made 0.5 to 5.0 Pa. Under the Ar gas atmosphere with the pressure of 0.5 to 5.0 Pa, a bias voltage with −200 to −1000V is applied to the substrate. A current with 5 to 20 A is passed through the tungsten filament in the reaction vessel. The surface of substrate is subjected to an ion bombardment treatment by an Ar gas. After the surface of the substrate is subjected to the ion bombardment treatment, the reaction vessel is evacuated so that a pressure inside thereof becomes 1×10⁻² Pa or lower.

Then, a reaction gas such as a nitrogen gas, etc., is introduced into the reaction vessel. By making the pressure in the reaction vessel 0.5 to 5.0 Pa, a bias voltage with −10 to −150V is applied to the substrate. By evaporating the metal evaporation sources depending on the metal components of the respective layers by an arc discharge, the respective layers can be formed onto the surface of the substrate. Incidentally, two or more kinds of metal evaporation sources placed in a position apart from each other are simultaneously evaporated by an arc discharge, and the table onto which a substrate has been fixed is rotated to form a layer constituting the first laminated structure or the second laminated structure. In this case, by adjusting a rotation number of the table onto which the substrate has been fixed in the reaction vessel, the thicknesses of the respective layers constituting the first laminated structure or the second laminated structure can be controlled. By alternately evaporating two or more kinds of metal evaporation sources by an arc discharge, a layer constituting the first laminated structure or the second laminated structure can be also formed. In this case, by adjusting arc discharge times of the metal evaporation sources respectively, the thicknesses of the respective layers constituting the first laminated structure or the second laminated structure can be controlled.

The thicknesses of the respective layers constituting the coating layer and the thicknesses of the respective laminated structures can be measured by observing the cross-sectional structure of the coated tool. For example, the thicknesses of the respective layers constituting the coating layer and the thicknesses of the respective laminated structures can be measured by using optical microscope, scanning electron microscope (SEM), transmission electron microscope (TEM), etc.

The average thicknesses of the respective layers constituting the coating layer and the average thicknesses of the respective laminated structures can be obtained as follows.

At the position nearer to 50 μm from the cutting edge of the surface opposed to the metal evaporation sources toward the center portion of said surface, the cross-sectional surface of the coated tool is observed at the three portions or more. From the observed cross-sectional surface, thicknesses of the respective layers and thicknesses of the respective laminated structure are measured. By calculating the average value of the measured thicknesses, the average thickness can be obtained.

The compositions of the respective layers of the coated tool of the present invention can be measured from the cross-sectional structure of the coated tool by using an energy dispersive X-ray spectrometry (EDS) or a wavelength dispersive X-ray spectrometry (WDS), etc.

A kind of the coated tool of the present invention may be specifically a tool for milling or turning. Examples of such a tool may be an indexable cutting insert, a drill and an end mill.

EXAMPLES Example 1

A cemented carbide corresponding to P10 with an ISO standard SEEN1203AGTN insert shape was prepared as the substrate. In the reaction vessel of an arc ion plating device, metal evaporation sources which became the compositions of the respective layers shown in Table 1 and Table 2 were arranged. The prepared substrate was fixed to fixing metal fitting of a rotary table in the reaction vessel.

Thereafter, inside the reaction vessel was evacuated until the pressure therein became 5.0×10⁻³ Pa or lower. After evacuation, the substrate was heated by a heater in the reaction vessel until the temperature thereof became 500° C. After heating, an Ar gas was introduced into the reaction vessel so that the pressure in the reaction vessel became 5.0 Pa.

At an Ar gas atmosphere with a pressure of 5.0 Pa, a bias voltage with −1,000V was applied to the substrate. A current of 10 A was passed through the tungsten filament in the reaction vessel. Under such conditions, the ion bombardment treatment by an Ar gas was carried out for 30 minutes to the surface of the substrate. After completion of the ion bombardment treatment, inside the reaction vessel was evacuated until the pressure in the reaction vessel became 5.0×10⁻³ Pa or lower.

After evacuation, a nitrogen gas was introduced into the reaction vessel, and inside the reaction vessel was made a nitrogen gas atmosphere with a pressure of 2.7 Pa. A bias voltage of −50V was applied to the substrate. The respective layers were formed by evaporating the metal evaporation sources by an arc discharge with an arc current of 200 A.

When Layer A1 and Layer B1 of Present products 1 to 9 and Comparative products 1 and 2 were to be formed, the metal evaporation sources of Layer A1 and the metal evaporation sources of Layer B1 were alternately evaporated by an arc discharge to form Layer A1 and Layer B1. At this time, the respective arc discharge times were so adjusted that Layer A1 and Layer B1 have the thicknesses shown in Table 3. In Comparative product 3 having a thick thickness of the layer, the metal evaporation sources of Layer X and the metal evaporation sources of Layer Y were similarly evaporated by the arc discharge alternately to form Layer X and Layer Y. At this time, the thickness of Layer X and the thickness of Layer Y were controlled by adjusting the arc discharge time at the time of forming the respective layers.

When Layer A2 and Layer B2 of Present products 1 to 9 and Comparative products 1 and 2 were to be formed, the metal evaporation sources of Layer A2 and the metal evaporation sources of Layer B2 were evaporated by an arc discharge simultaneously to form Layer A2 and Layer B2. At this time, the number of rotation of the table was adjusted within the range of 0.2 to 10 min⁻¹ so that Layer A2 and Layer B2 have the thicknesses shown in Table 3. In Comparative product 4 having a thin thickness of the layers, the metal evaporation sources of Layer X and the metal evaporation sources of Layer Y were similarly evaporated by the arc discharge simultaneously to form Layer X and Layer Y. At this time, the thickness of Layer X and the thickness of Layer Y were controlled by adjusting the number of rotation of the table within the range of 0.2 to 10 min⁻¹.

Comparative product 5 is constituted by layers having a thin thickness and layers having a thick thickness alternately laminated. The thicknesses of the layers constituting Comparative product 5 were controlled by adjusting the arc discharge time and the number of rotation of the table. The number of rotation of the table was adjusted within the range of 0.2 to 10 min⁻¹.

The monolayer of Comparative product 6 was formed by evaporating the metal evaporation sources by an arc discharge with an arc current of 200 A while applying a bias voltage of −50V to the substrate.

The respective layers were formed onto the surface of the substrate until the layers became predetermined thicknesses shown in Table 3 and Table 4. Thereafter, a power of the heater was turned off, and after the temperature of the sample became 100° C. or lower, the sample was taken out from the reaction vessel.

TABLE 1 First laminated structure Second laminated structure LAYER A1 LAYER B1 LAYER A2 LAYER B2 Sample No. Composition Composition Composition Composition Present (Ti_(0.50)Al_(0.50))N (Ti_(0.67)Al_(0.33))N (Ti_(0.50)Al_(0.50))N (Ti_(0.67)Al_(0.33))N product 1 Present (Ti_(0.50)Al_(0.50))N (Ti_(0.67)Al_(0.33))N (Ti_(0.50)Al_(0.50))N (Ti_(0.67)Al_(0.33))N product 2 Present (Ti_(0.50)Al_(0.50))N (Ti_(0.67)Al_(0.33))N (Ti_(0.50)Al_(0.50))N (Ti_(0.67)Al_(0.33))N product 3 Present (Ti_(0.50)Al_(0.50))N (Ti_(0.67)Al_(0.33))N (Ti_(0.50)Al_(0.50))N (Ti_(0.67)Al_(0.33))N product 4 Present (Ti_(0.50)Al_(0.50))N (Ti_(0.33)Al_(0.67))N (Ti_(0.50)Al_(0.50))N (Ti_(0.33)Al_(0.67))N product 5 Present (Ti_(0.50)Al_(0.50))N (Ti_(0.33)Al_(0.67))N (Ti_(0.50)Al_(0.50))N (Ti_(0.33)Al_(0.67))N product 6 Present (Ti_(0.67)Al_(0.33))N (Ti_(0.33)Al_(0.67))N (Ti_(0.67)Al_(0.33))N (Ti_(0.33)Al_(0.67))N product 7 Present (Ti_(0.67)Al_(0.33))N (Ti_(0.33)Al_(0.67))N (Ti_(0.67)Al_(0.33))N (Ti_(0.33)Al_(0.67))N product 8 Present (Ti_(0.50)Al_(0.50))N (Ti_(0.67)Al_(0.33))N (Ti_(0.50)Al_(0.50))N (Ti_(0.67)Al_(0.33))N product 9 Comparative (Ti_(0.50)Al_(0.50))N (Ti_(0.67)Al_(0.33))N (Ti_(0.50)Al_(0.50))N (Ti_(0.67)Al_(0.33))N product 1 Comparative (Ti_(0.67)Al_(0.33))N (Ti_(0.33)Al_(0.67))N (Ti_(0.67)Al_(0.33))N (Ti_(0.33)Al_(0.67))N product 2

TABLE 2 Coating layer Alternate laminate Average thickness LAYER X and LAYER Y Composition LAYER LAYER Repeated Total LAYER LAYER X Y times thickness Sample No. X Y (nm) (nm) (times) (μm) Comparative (Ti_(0.50)Al_(0.50))N (Ti_(0.67)Al_(0.33))N 150 150 15 4.50 product 3 Comparative (Ti_(0.67)Al_(0.33))N (Ti_(0.50)Al_(0.50))N 20 20 110 4.40 product 4 Comparative (Ti_(0.67)Al_(0.33))N (Ti_(0.33)Al_(0.67))N 5 80 50 4.25 product 5 Comparative (Ti_(0.50)Al_(0.50))N Monolayer 4.50 product 6

TABLE 3 First laminated structure Second laminated structure LAYER A1 LAYER B1 LAYER A2 LAYER B2 Average Average Average Average thickness thickness thickness thickness Sample No. (nm) (nm) (nm) (nm) Present 100 100 10 10 product 1 Present 60 60 2 2 product 2 Present 250 250 10 10 product 3 Present 100 100 55 55 product 4 Present 300 300 50 50 product 5 Present 200 200 2 2 product 6 Present 100 100 10 10 product 7 Present 80 80 2 2 product 8 Present 150 150 30 30 product 9 Comparative 100 100 10 10 product 1 Comparative 200 200 2 2 product 2

TABLE 4 Coating layer First layer (Substrate side) Second layer LAYER A1 + LAYER B1 LAYER A2 + LAYER B2 Third layer Fourth layer Average Average LAYER A1 + LAYER B1 LAYER A2 + LAYER B2 Lami- Re- thick- Lami- Re- thick- Lami- Re- Average Lami- Re- Average nated peated ness nated peated ness nated peated thick- nated peated thick- Sample struc- times (μm) struc- times (μm) struc- times ness struc- times ness No. ture (times) TA1 ture (times) TA2 ture (times) (μm) ture (times) (μm) Present First 2 0.40 Second 10 0.20 First 4 0.80 Second 30 0.60 product 1 Present First 4 0.48 Second 60 0.24 First 6 0.72 Second 160 0.64 product 2 Present First 2 1.00 Second 20 0.40 First 4 2.00 Second 50 1.00 product 3 Present First 2 0.40 Second 5 0.55 First 4 0.80 Second 10 1.10 product 4 Present First 4 2.40 Second 15 1.50 First 8 4.80 Second 30 3.00 product 5 Present First 2 0.80 Second 10 0.04 First 4 1.60 Second 28 0.11 product 6 Present First 2 0.40 Second 70 1.40 First 6 1.20 Second 300 6.00 product 7 Present First 2 0.32 Second 4 0.02 First 8 1.28 Second 16 0.06 product 8 Present First 2 0.60 Second 10 0.60 First 3 0.90 Second 10 0.60 product 9 Comparative First 5 1.00 Second 50 1.00 First 5 1.00 Second 50 1.00 product 1 Comparative First 3 1.20 Second 50 0.20 First 3 1.20 Second 50 0.20 product 2 Coating layer Fifth layer Sixth layer (Surface side) LAYER A1 + LAYER B1 LAYER A2 + LAYER B2 Average Average Lami- Re- thick- Lami- Re- thick- Total nated peated ness nated peated ness thick- Sample struc- times (μm) struc- times (μm) ness No. ture (times) TB1 ture (times) TB2 (μm) Present First 6 1.20 Second 50 1.00 4.20 product 1 Present First 8 0.96 Second 260  1.04 4.08 product 2 Present — — — — — — 4.40 product 3 Present First 6 1.20 Second 20 2.20 6.25 product 4 Present — — — — — — 11.70 product 5 Present First 15  6.00 Second 120  0.48 9.03 product 6 Present — — — — — — 9.00 product 7 Present — — — — — — 1.68 product 8 Present First 10  3.00 Second 10 0.60 6.30 product 9 Comparative First 5 1.00 Second 50 1.00 6.00 product 1 Comparative First 3 1.20 Second 50 0.20 4.20 product 2 *“First” and “Second” at the column of “Laminated structure” mean the first laminated structure and the second laminated structure of the Present product and the Comparative product with the corresponding number in Tables 1 to 3.

TABLE 5 First laminated structure Second laminated structure Average thickness Average thickness Substrate side/ Increase in Substrate side/ Increase in Surface side (%) average Surface side (%) average Sample No. (TA1/TB1) × 100 thickness (TA2/TB2) × 100 thickness Present 33 Continuous 20 Continuous product 1 Present 50 Continuous 23 Continuous product 2 Present 50 Stepwise 40 Stepwise product 3 Present 33 Continuous 25 Continuous product 4 Present 50 Continuous 50 Continuous product 5 Present 13 Stepwise 8 Stepwise product 6 Present 33 Stepwise 23 Stepwise product 7 Present 25 Stepwise 25 Stepwise product 8 Present 20 Stepwise 100 Not product 9 increased Comparative 100 Not 100 Not product 1 increased increased Comparative 100 Not 100 Not product 2 increased increased

The average thickness of the respective layers and the average thickness of the respective laminated structures of the obtained samples were obtained as follows.

Cross-sectional surfaces at the three portions were observed by TEM at the neighbor of the position of 50 μm from the cutting edge at the surface opposed to the metal evaporation sources of the coated tool toward the center portion of said surface. The thicknesses of the respective layers and the thicknesses of the respective laminated structures were measured, and an average value of the measured thicknesses was calculated.

The compositions of the respective layers of the obtained samples were obtained as follows.

The compositions were measured by using EDS at the cross-sectional surface at the position of 50 μm from the cutting edge at the surface opposed to the metal evaporation sources of the coated tool toward the center portion of said surface.

These measured results are also shown in Tables 1 to 4.

Incidentally, compositional ratios of metal elements of the respective layers in Tables 1 to 4 show an atomic ratio of the respective metal elements based on the whole metal elements in the metal compounds constituting the respective layers.

From the average thickness of the first laminated structure shown in Table 4, a ratio of the average thickness of the first laminated structure nearest to the substrate based on the average thickness of the first laminated structure nearest to the surface of the coating layer was obtained. Similarly, from the average thickness of the second laminated structure shown in Table 4, a ratio of the average thickness of the second laminated structure nearest to the substrate based on the average thickness of the second laminated structure nearest to the surface of the coating layer was obtained. These results are shown in Table 5.

By using the obtained samples, the following Cutting test 1 and Cutting test 2 were carried out, and fracture resistance and wear resistance were evaluated. The evaluation results are shown in Table 6.

[Cutting test 1: Evaluation of fracture resistance]

-   Work piece material: SCM440, -   Shape of work piece material: a rectangular parallelepiped with 105     mm×220 mm×60 mm (provided that six holes with a diameter of φ 40 mm     have been drilled at the surface with 105 mm×220 mm of the     rectangular parallelepiped at which face milling processing is to be     carried out.) -   Cutting speed: 240 m/min, -   Feed: 0.4 mm/tooth, -   Depth of cut: 2.0 mm, -   Cutting width: 105 mm, -   Coolant: none, -   Cutter effective diameter: φ 125 mm, -   Evaluation item: A processed length until the sample had been     defected (defect is generated at the cutting blade portion of the     sample) was measured as the tool life. A processed length until the     sample had fractured was measured.

[Cutting test 2: Evaluation of wear resistance]

-   Work piece material: SCM440, -   Shape of work piece material: a rectangular parallelepiped with 105     mm×220 mm×60 mm, -   Cutting speed: 270 m/min, -   Feed: 0.12 mm/tooth, -   Depth of cut: 2.0 mm, -   Cutting width: 50 mm, -   Coolant: none, -   Cutter effective diameter: φ 100 mm, -   Evaluation item: A processed length until the maximum flank wear     width had become 0.2 mm was the tool life. The processed length     until the maximum flank wear width had reached 0.2 mm was measured.

Evaluation standard of the processed length until the tool reaches its tool life in Cutting test 1 is as follows.

-   ⊚: 10.5 m or more -   ◯: 10 m or more and less than 10.5 m -   Δ: 9.5 m or more and less than 10 m -   x: Less than 9.5 m

Evaluation standard of the processed length until the tool reaches its tool life in Cutting test 2 is as follows.

-   ⊚: 6 m or more -   ◯: 5.5 m or more and less than 6 m -   Δ: 5 m or more and less than 5.5 m -   x: Less than 5 m

An order of the evaluation is (Excellent) ⊚>◯>Δ> x (Poor). The evaluation of ⊚ or ◯ means that cutting performance is excellent. The results of the obtained total evaluation are shown in Table 6.

TABLE 6 Cutting test 1 Cutting test 2 Wear resistance test Fracture resistance test Tool life Tool life Sample No. (m) Evaluation (m) Evaluation Present product 1 10.1 ◯ 5.7 ◯ Present product 2 10.0 ◯ 5.8 ◯ Present product 3 10.0 ◯ 5.7 ◯ Present product 4 10.4 ◯ 6.2 ⊚ Present product 5 11.4 ⊚ 6.5 ⊚ Present product 6 12.2 ⊚ 6.0 ⊚ Present product 7 10.9 ⊚ 7.4 ⊚ Present product 8 11.4 ⊚ 5.5 ◯ Present product 9 10.3 ◯ 5.9 ◯ Comparative product 1 9.5 Δ 5.7 ◯ Comparative product 2 9.5 Δ 5.5 ◯ Comparative product 3 8.7 X 5.0 Δ Comparative product 4 9.1 X 4.8 X Comparative product 5 9.1 X 4.7 X Comparative product 6 7.8 X 4.2 X

From the results of Table 6, the results of the wear resistance test of Present products were all ⊚ or ◯. The results of the wear resistance test of Comparative products were Δ or x. Accordingly, it can be understood that Present products are excellent in wear resistance than Comparative products. In addition, the results of the fracture resistance test of Present products were all ◯ or higher. The results of the fracture resistance test of Comparative products were ◯, Δ or x. From these results, it can be understood that Present products have equal fracture resistance to those of Comparative products or more in the point of not evaluated to as Δ or x. From these results, it can be understood that tool lives of Present products are elongated. As can be seen from these results, according to the present invention, wear resistance could be improved without lowering fracture resistance of the coated tool.

Example 2

A cemented carbide corresponding to P10 with an ISO standard SEEN1203AGTN insert shape was prepared as the substrate. In the reaction vessel of an arc ion plating device, metal evaporation sources which became the compositions of the respective layers shown in Table 7 were arranged. According to the same preparation method as in Example 1, the samples having layer constitutions shown in Tables 8 and 9 were prepared.

Present product 10 and Comparative product 10 were prepared as follows.

In the reaction vessel of the arc ion plating device, metal evaporation sources which became the compositions of the respective layers shown in Table 7 were arranged. A mixed gas of an N₂ gas and a CH₄ gas was introduced into the reaction vessel. A partial pressure ratio of the N₂ gas and the CH₄ gas in the mixed gas is N₂:CH₄=1:1. A pressure in the reaction vessel is 2.7 Pa. The respective layers were prepared in the same manner as in Example 1 except for setting the atmosphere in the reaction vessel as mentioned above, and the samples having layer constitutions shown in Tables 8 and 9 were prepared.

Present product 18 was prepared as follows.

In the reaction vessel of the arc ion plating device, metal evaporation sources which became the compositions of the respective layers shown in Table 7 were arranged. When an oxide layer was to be formed, an O₂ gas was introduced into the reaction vessel, and a pressure in the reaction vessel was controlled to 2.7 Pa. Thereafter, when a nitride layer was to be formed, the O₂ gas was exhausted from the reaction vessel, an N₂ gas was introduced into the reaction vessel, and a pressure in the reaction vessel was controlled to 2.7 Pa. The samples having layer constitutions shown in Tables 8 and 9 were prepared in the same manner as in Example 1 except for setting the atmosphere in the reaction vessel as mentioned above.

TABLE 7 First laminated structure Second laminated structure LAYER A1 LAYER B1 LAYER A2 LAYER B2 Sample No. Composition Composition Composition Composition Present (Ti_(0.50)Al_(0.50))CN (Ti_(0.67)Al_(0.33))CN (Ti_(0.50)Al_(0.50))CN (Ti_(0.67)Al_(0.33))CN product 10 Present (Ti_(0.50)Al_(0.50))N (Al_(0.45)Ti_(0.45)Si_(0.10))N (Ti_(0.50)Al_(0.50))N (Al_(0.45)Ti_(0.45)Si_(0.10))N product 11 Present (Ti_(0.50)Al_(0.50))N (Al_(0.45)Ti_(0.45)Sr_(0.10))N (Ti_(0.50)Al_(0.50))N (Al_(0.45)Ti_(0.45)Sr_(0.10))N product 12 Present (Ti_(0.50)Al_(0.50))N (Al_(0.45)Ti_(0.45)Y_(0.10))N (Ti_(0.50)Al_(0.50))N (Al_(0.45)Ti_(0.45)Y_(0.10))N product 13 Present (Ti_(0.50)Al_(0.50))N (Al_(0.50)Ti_(0.30)Cr_(0.20))N (Ti_(0.50)Al_(0.50))N (Al_(0.50)Ti_(0.30)Cr_(0.20))N product 14 Present (Ti_(0.50)Al_(0.50))N (Al_(0.50)Ti_(0.45)Nb_(0.05))N (Ti_(0.50)Al_(0.50))N (Al_(0.50)Ti_(0.45)Nb_(0.05))N product 15 Present (Ti_(0.67)Al_(0.33))N (Al_(0.50)Ti_(0.45)Ta_(0.05))N (Ti_(0.67)Al_(0.33))N (Al_(0.50)Ti_(0.45)Ta_(0.05))N product 16 Present (Ti_(0.67)Al_(0.33))N (Al_(0.50)Ti_(0.45)W_(0.05))N (Ti_(0.67)Al_(0.33))N (Al_(0.50)Ti_(0.45)W_(0.05))N product 17 Present (Al_(0.50)Cr_(0.50))₂O₃ (Ti_(0.90)Si_(0.10))N (Al_(0.50)Cr_(0.50))₂O₃ (Ti_(0.90)Si_(0.10))N product 18 Present (Ti_(0.50)Al_(0.50))N (Al_(0.50)Cr_(0.50))N (Ti_(0.50)Al_(0.50))N (Al_(0.50)Cr_(0.50))N product 19 Present TiN (Ti_(0.40)Al_(0.30)Cr_(0.20)Si_(0.10))N TiN (Ti_(0.40)Al_(0.30)Cr_(0.20)Si_(0.10))N product 20 Comparative (Ti_(0.50)Al_(0.50))N (Al_(0.50)Ti_(0.30)Cr_(0.20))N (Ti_(0.50)Al_(0.50))N (Al_(0.50)Ti_(0.30)Cr_(0.20))N product 7 Comparative TiN (Ti_(0.40)Al_(0.30)Cr_(0.20)Si_(0.10))N TiN (Ti_(0.40)Al_(0.30)Cr_(0.20)Si_(0.10))N product 8 Comparative (Ti_(0.67)Al_(0.33))N (Ti_(0.90)Si_(0.10))N (Ti_(0.67)Al_(0.33))N (Ti_(0.90)Si_(0.10))N product 9 Comparative (Ti_(0.50)Al_(0.50))CN (Ti_(0.67)Al_(0.33))CN (Ti_(0.50)Al_(0.50))CN (Ti_(0.67)Al_(0.33))CN product 10

TABLE 8 First laminated structure Second laminated structure LAYER A1 LAYER B1 LAYER A2 LAYER B2 Average Average Average Average thickness thickness thickness thickness Sample No. (nm) (nm) (nm) (nm) Present 110 110 10 10 product 10 Present 110 110 10 10 product 11 Present 110 110 10 10 product 12 Present 110 110 10 10 product 13 Present 110 110 10 10 product 14 Present 110 110 10 10 product 15 Present 110 110 10 10 product 16 Present 110 110 10 10 product 17 Present 110 110 10 10 product 18 Present 110 110 10 10 product 19 Present 110 110 10 10 product 20 Comparative 110 110 10 10 product 7 Comparative 110 110 10 10 product 8 Comparative 110 110 10 10 product 9 Comparative 110 110 10 10 product 10

TABLE 9 Coating layer First layer (Substrate side) Second layer LAYER A1 and LAYER B1 LAYER A2 and LAYER B2 Third layer Fourth layer Average Average LAYER A1 and LAYER B1 LAYER A2 and LAYER B2 Lami- Re- thick- Lami- Re- thick- Lami- Re- Average Lami- Re- Average nated peated ness nated peated ness nated peated thick- nated peated thick- Sample struc- times (μm) struc- times (μm) struc- times ness struc- times ness No. ture (times) TA1 ture (times) TA2 ture (times) (μm) ture (times) (μm) Present First 2 0.44 Second 10 0.20 First 4 0.88 Second 40 0.80 product 10 Present First 2 0.44 Second 10 0.20 First 4 0.88 Second 40 0.80 product 11 Present First 2 0.44 Second 10 0.20 First 4 0.88 Second 40 0.80 product 12 Present First 2 0.44 Second 10 0.20 First 4 0.88 Second 40 0.80 product 13 Present First 2 0.44 Second 10 0.20 First 4 0.88 Second 40 0.80 product 14 Present First 2 0.44 Second 10 0.20 First 4 0.88 Second 40 0.80 product 15 Present First 2 0.44 Second 10 0.20 First 4 0.88 Second 40 0.80 product 16 Present First 2 0.44 Second 10 0.20 First 4 0.88 Second 40 0.80 product 17 Present First 2 0.44 Second 10 0.20 First 4 0.88 Second 40 0.80 product 18 Present First 4 0.88 Second 10 0.20 First 4 0.88 Second 40 0.80 product 19 Present First 2 0.44 Second 10 0.20 First 4 0.88 Second 40 0.80 product 20 Comparative First 4 0.88 Second 40 0.80 First 4 0.88 Second 40 0.80 product 7 Comparative First 4 0.88 Second 40 0.80 First 4 0.88 Second 40 0.80 product 8 Comparative First 4 0.88 Second 40 0.80 First 4 0.88 Second 40 0.80 product 9 Comparative First 4 0.88 Second 40 0.80 First 4 0.88 Second 40 0.80 product 10 Coating layer Fifth layer Sixth layer (Surface side) LAYER A1 and LAYER B1 LAYER A2 and LAYER B2 Average Average Lami- Re- thick- Lami- Re- thick- Total nated peated ness nated peated ness thick- Sample struc- times (μm) struc- times (μm) ness No. ture (times) TB1 ture (times) TB2 (μm) Present First 6 1.32 Second 70 1.40 5.04 product 10 Present First 6 1.32 Second 70 1.40 5.04 product 11 Present First 6 1.32 Second 70 1.40 5.04 product 12 Present First 6 1.32 Second 70 1.40 5.04 product 13 Present First 6 1.32 Second 70 1.40 5.04 product 14 Present First 6 1.32 Second 70 1.40 5.04 product 15 Present First 6 1.32 Second 70 1.40 5.04 product 16 Present First 6 1.32 Second 70 1.40 5.04 product 17 Present First 6 1.32 Second 70 1.40 5.04 product 18 Present First 4 0.88 Second 70 1.40 5.04 product 19 Present First 6 1.32 Second 70 1.40 5.04 product 20 Comparative First 4 0.88 Second 40 0.80 5.04 product 7 Comparative First 4 0.88 Second 40 0.80 5.04 product 8 Comparative First 4 0.88 Second 40 0.80 5.04 product 9 Comparative First 4 0.88 Second 40 0.80 5.04 product 10 *“First” and “Second” at the column of “Laminated structure” mean the first laminated structure and the second laminated structure of the Present product with the corresponding number in Table 7 and Table 8.

TABLE 10 First laminated structure Second laminated structure Average thickness Average thickness Substrate side/ Increase in Substrate side/ Increase in Surface side (%) average Surface side (%) average Sample No. (TA1/TB1) × 100 thickness (TA2/TB2) × 100 thickness Present 33 Continuous 14 Continuous product 10 Present 33 Continuous 14 Continuous product 11 Present 33 Continuous 14 Continuous product 12 Present 33 Continuous 14 Continuous product 13 Present 33 Continuous 14 Continuous product 14 Present 33 Continuous 14 Continuous product 15 Present 33 Continuous 14 Continuous product 16 Present 33 Continuous 14 Continuous product 17 Present 33 Continuous 14 Continuous product 18 Present 100 Not 14 Continuous product 19 increased Present 33 Continuous 14 Continuous product 20 Comparative 100 Not 100 Not product 7 increased increased Comparative 100 Not 100 Not product 8 increased increased Comparative 100 Not 100 Not product 9 increased increased Comparative 100 Not 100 Not product 10 increased increased

The average thicknesses of the respective layers and the compositions of the respective layers of the obtained samples were measured in the same manner as in Example 1. These results are shown in Tables 7 to 10. In addition, Cutting test 1 and Cutting test 2 which were the same as in Example 1 were carried out by using the obtained samples to evaluate wear resistance and fracture resistance. The evaluation results are shown in Table 11.

Evaluation standard of the processed length until the tool reaches its tool life in Cutting test 1 is as follows.

-   ⊚: 10.5 m or more -   ◯: 10 m or more and less than 10.5 m -   Δ: 9.5 m or more and less than 10 m -   X: Less than 9.5 m

Evaluation standard of the processed length until the tool reaches its tool life in Cutting test 2 is as follows.

-   ⊚: 6 m or more -   ◯: 5.5 m or more and less than 6 m -   Δ: 5 m or more and less than 5.5 m -   X: Less than 5 m

An order of the evaluation is (Excellent) ⊚>◯>Δ> X (Poor). The evaluation of ⊚ or ◯ means that cutting performance is excellent. The results of the obtained total evaluation are shown in Table 11

TABLE 11 Cutting test 1 Cutting test 2 Wear resistance test Fracture resistance test Tool life Tool life Sample No. (m) Evaluation (m) Evaluation Present product 10 10.4 ◯ 6.3 ⊚ Present product 11 10.8 ⊚ 5.9 ◯ Present product 12 10.5 ⊚ 6.2 ⊚ Present product 13 10.4 ◯ 6.1 ⊚ Present product 14 10.5 ⊚ 6.0 ⊚ Present product 15 10.6 ⊚ 5.8 ◯ Present product 16 10.6 ⊚ 5.9 ◯ Present product 17 10.8 ⊚ 6.2 ⊚ Present product 18 10.3 ◯ 6.1 ⊚ Present product 19 10.1 ◯ 5.9 ◯ Present product 20 10.5 ⊚ 6.1 ⊚ Comparative product 7 9.6 Δ 5.9 ◯ Comparative product 8 9.2 X 5.5 ◯ Comparative product 9 9.5 Δ 5.7 ◯ Comparative product 10 9.2 X 5.9 ◯

From the results of Table 11, the results of the wear resistance test of Present products were all ⊚ or ◯. The results of the wear resistance test of Comparative products were Δ or x. From these results, it can be understood that Present products are superior in wear resistance to those of Comparative products. In addition, the results of the fracture resistance test of Present products were all ◯ or higher, and there were ⊚. The results of the fracture resistance test of Present products were equal to Comparative products or more in the point that there were ⊚. From these results, it can be understood that Present products were excellent in fracture resistance than those of Comparative products. From these results, it can be understood that tool lives of Present products are elongated. As can be seen from these results, according to the present invention, wear resistance could be improved without lowering fracture resistance of the coated tool.

Example 3

Present products 21 to 27 and Comparative products 11 to 13 were prepared as follows.

A cemented carbide corresponding to P10 with an ISO standard SEEN1203AGTN insert shape was prepared as the substrate. In the reaction vessel of an arc ion plating device, metal evaporation sources which became the compositions of the respective layers shown in Table 12 and Table 13 were arranged. According to the same preparation method as in Example 1, the samples having layer constitutions shown in Tables 13, 14 and 16 were prepared.

TABLE 12 First laminated structure Second laminated structure LAYER A1 LAYER B1 LAYER A2 LAYER B2 Sample No. Composition Composition Composition Composition Present (Ti_(0.50)Al_(0.50))N (Ti_(0.67)Al_(0.33))N (Ti_(0.50)Al_(0.50))N (Ti_(0.67)Al_(0.33))N product 21 Present (Ti_(0.50)Al_(0.50))N (Ti_(0.67)Al_(0.33))N (Ti_(0.50)Al_(0.50))N (Ti_(0.67)Al_(0.33))N product 22 Present (Ti_(0.50)Al_(0.50))N (Al_(0.50)Ti_(0.30)Cr_(0.20))N (Ti_(0.50)Al_(0.50))N (Al_(0.50)Ti_(0.30)Cr_(0.20))N product 23 Present (Ti_(0.67)Al_(0.33))N (Al_(0.50)Ti_(0.45)W_(0.05))N (Ti_(0.67)Al_(0.33))N (Al_(0.50)Ti_(0.45)W_(0.05))N product 24 Present (Al_(0.50)Cr_(0.50))N (Ti_(0.90)Si_(0.10))N (Al_(0.50)Cr_(0.50))N (Ti_(0.90)Si_(0.10))N product 25 Present (Ti_(0.50)Al_(0.50))N (Al_(0.50)Ti_(0.45)Nb_(0.05))N (Ti_(0.50)Al_(0.50))N (Al_(0.50)Ti_(0.45)Nb_(0.05))N product 26 Present (Ti_(0.50)Al_(0.50))N (Ti_(0.40)Al_(0.30)Cr_(0.20)Si_(0.10))N (Ti_(0.50)Al_(0.50))N (Ti_(0.40)Al_(0.30)Cr_(0.20)Si_(0.10))N product 27

TABLE 13 Coating layer Alternately laminated layers First layer Second layer Third layer LAYER X LAYER X LAYER X Average and and and thickness LAYER Y Average thickness LAYER Y Average thickness LAYER Y Total Composition LAYER LAYER Repeated LAYER LAYER Repeated LAYER LAYER Repeated thick- Sample LAYER LAYER X Y times X Y times X Y times ness No. X Y (nm) (nm) (times) (nm) (nm) (times) (nm) (nm) (times) (μm) Comparative (Ti_(0.50)Al_(0.50))N (Ti_(0.67)Al_(0.33))N 70 70 10 80 80 10 90 90 10 4.80 product 11 Comparative (Ti_(0.67)Al_(0.33))N (Ti_(0.50)Al_(0.50))N 25 25 18 45 45 18 65 65 18 4.86 product 12 Comparative (Ti_(0.67)Al_(0.33))N (Ti_(0.33)Al_(0.67))N 20 20 15 35 35 20 60 60 25 5.00 product 13

TABLE 14 First layer (Substrate side) Second layer First laminated Second laminated Third layer structure structure First laminated LAYER A1 LAYER A2 structure Average LAYER B1 Average LAYER B2 LAYER A1 LAYER B1 thickness Average thickness Average Average Average Sample (nm) thickness (nm) thickness thickness thickness No. TC1 (nm) TC2 (nm) (nm) (nm) Present 60 60 10 10 80 80 product 21 Present 60 60 10 10 150 150 product 22 Present 60 60 2 2 80 80 product 23 Present 60 60 10 10 80 80 product 24 Present 60 60 5 5 65 65 product 25 Present 70 70 10 10 70 70 product 26 Present 40 40 20 20 60 60 product 27 Sixth layer Fifth layer (Surface side) Fourth layer First laminated Second laminated Second laminated structure structure structure LAYER A1 LAYER A2 LAYER A2 LAYER B2 Average LAYER B1 Average LAYER B2 Average Average thickness Average thickness Average Sample thickness thickness (nm) thickness (nm) thickness No. (nm) (nm) TD1 (nm) TD2 (nm) Present 20 20 100 100 30 30 product 21 Present 30 30 — — — — product 22 Present 10 10 100 100 40 40 product 23 Present 20 20 200 200 30 30 product 24 Present 10 10 70 70 20 20 product 25 Present 20 20 70 70 30 30 product 26 Present 20 20 80 80 20 20 product 27

TABLE 15 First laminated structure Second laminated structure Average thickness Average thickness of respective layers Increase in of respective layers Increase in Substrate side/ average thickness Substrate side/ average thickness Surface side (%) of respective Surface side (%) of respective Sample No. (TC1/TD1) × 100 layers (TC2/TD2) × 100 layers Present 60 Continuous 33 Continuous product 21 Present 40 Stepwise 33 Stepwise product 22 Present 60 Continuous 5 Stepwise product 23 Present 30 Stepwise 33 Continuous product 24 Present 86 Continuous 25 Stepwise product 25 Present 100 Not 33 Continuous product 26 increased Present 50 Continuous 100 Not product 27 increased

TABLE 16 Coating layer First layer (Substrate side) Second layer LAYER A1 and LAYER B1 LAYER A2 and LAYER B2 Third layer Fourth layer Average Average LAYER A1 and LAYER B1 LAYER A2 and LAYER B2 Lami- Re- thick- Lami- Re- thick- Lami- Re- Average Lami- Re- Average nated peated ness nated peated ness nated peated thick- nated peated thick- Sample struc- times (μm) struc- times (μm) struc- times ness struc- times ness No. ture (times) TA1 ture (times) TA2 ture (times) (μm) ture (times) (μm) Present First 2 0.24 Second 10 0.20 First 4 0.64 Second 20 0.80 product 21 Present First 4 0.48 Second 20 0.40 First 6 1.80 Second 40 2.40 product 22 Present First 2 0.24 Second 20 0.08 First 3 0.48 Second 30 0.60 product 23 Present First 2 0.24 Second 5 0.10 First 3 0.48 Second 15 0.60 product 24 Present First 3 0.36 Second 20 0.20 First 7 0.91 Second 30 0.60 product 25 Present First 2 0.28 Second 10 0.20 First 4 0.56 Second 20 0.80 product 26 Present First 2 0.16 Second 10 0.40 First 4 0.48 Second 35 1.40 product 27 Coating layer Fifth layer Sixth layer (Surface side) LAYER A1 and LAYER B1 LAYER A2 and LAYER B2 Average Average Lami- Re- thick- Lami- Re- thick- Total nated peated ness nated peated ness thick- Sample struc- times (μm) struc- times (μm) ness No. ture (times) TB1 ture (times) TB2 (μm) Present First 6 1.20 Second 40 2.40 5.48 product 21 Present — — — — — — 5.08 product 22 Present First 4 0.80 Second 40 3.20 5.40 product 23 Present First 8 3.20 Second 20 1.20 5.82 product 24 Present First 10  1.40 Second 40 1.60 5.07 product 25 Present First 6 0.84 Second 40 2.40 5.08 product 26 Present First 6 0.96 Second 40 1.60 5.00 product 27 *“First” and “Second” at the column of “Laminated structure” mean the first laminated structure and the second laminated structure of the Present product with the corresponding number in Table 12 and Table 14.

TABLE 17 First laminated structure Second laminated structure Average thickness Average thickness Substrate side/ Increase in Substrate side/ Increase in Surface side (%) average Surface side (%) average Sample No. (TA1/TB1) × 100 thickness (TA2/TB2) × 100 thickness Present 20 Continuous 8 Stepwise product 21 Present 27 Stepwise 17 Stepwise product 22 Present 30 Continuous 3 Continuous product 23 Present 8 Stepwise 8 Stepwise product 24 Present 26 Stepwise 13 Continuous product 25 Present 33 Continuous 8 Stepwise product 26 Present 17 Continuous 25 Stepwise product 27

The average thicknesses of the respective layers and the compositions of the respective layers of the obtained samples were measured in the same manner as in Example 1. These results are shown in Table 12 to 17. In addition, Cutting test 1 and Cutting test 2 which were the same as in Example 1 were carried out by using the obtained samples to evaluate wear resistance and fracture resistance. The evaluation results are shown in Table 18.

Evaluation standard of the processed length until the tool reaches its tool life in Cutting test 1 is as follows.

-   ⊚: 10.5 m or more -   ◯: 10 m or more and less than 10.5 m -   Δ: 9.5 m or more and less than 10 m -   x: Less than 9.5 m

Evaluation standard of the processed length until the tool reaches its tool life in Cutting test 2 is as follows.

-   ⊚: 6 m or more -   ◯: 5.5 m or more and less than 6 m -   Δ: 5 m or more and less than 5.5 m -   x: Less than 5 m

An order of the evaluation is (Excellent) ⊚>◯>Δ> x (Poor). The evaluation of ⊚ or ◯ means that cutting performance is excellent. The results of the obtained total evaluation are shown in Table 18

TABLE 18 Cutting test 1 Cutting test 2 Wear resistance test Fracture resistance test Tool life Tool life Sample No. (m) Evaluation (m) Evaluation Present 10.5 ⊚ 5.9 ◯ product 21 Present 10.4 ◯ 5.8 ◯ product 22 Present 10.3 ◯ 6.1 ⊚ product 23 Present 10.8 ⊚ 5.7 ◯ product 24 Present 10.5 ⊚ 5.9 ◯ product 25 Present 10.2 ◯ 6.0 ⊚ product 26 Present 10.4 ◯ 6.1 ⊚ product 27 Comparative 9.5 Δ 5.3 Δ product 11 Comparative 9.6 Δ 5.2 Δ product 12 Comparative 9.3 X 5.0 Δ product 13

From the results of Table 18, the results of the wear resistance test of Present products were all ⊚ or ◯. The results of the wear resistance test of Comparative products were all Δ or x. From these results, it can be understood that Present products are excellent in wear resistance than Comparative products. In addition, the results of the fracture resistance test of Present products were all ◯ or higher. The results of the fracture resistance test of Comparative products were all Δ. From these results, it can be understood that Present products are excellent in fracture resistance than Comparative products. From these results, it can be understood that tool lives of Present products are elongated. As can be seen from these results, according to the present invention, wear resistance could be improved without lowering fracture resistance of the coated tool.

Example 4

Present products 28 to 30 were prepared as follows.

A cemented carbide corresponding to P10 with an ISO standard SEEN1203AGTN insert shape was prepared as the substrate. In the reaction vessel of an arc ion plating device, metal evaporation sources which became the compositions of the respective layers shown in Table 19 were arranged. According to the same preparation method as in Example 1, the samples having layer constitutions shown in Table 20 and Table 21 were prepared.

TABLE 19 First laminated Second laminated Lower structure structure Upper layer LAYER A1 LAYER B1 LAYER A2 LAYER B2 layer Sample No. Composition Composition Composition Composition Composition Composition Present (Al_(0.50)Ti_(0.30)Cr_(0.20))N (Ti_(0.50)Al_(0.50))N (Ti_(0.67)Al_(0.33))N (Ti_(0.50)Al_(0.50))N (Ti_(0.67)Al_(0.33))N (Al_(0.50)Ti_(0.30)Cr_(0.20))N product 28 Present TiN (Ti_(0.50)Al_(0.50))N (Ti_(0.67)Al_(0.33))N (Ti_(0.50)Al_(0.50))N (Ti_(0.67)Al_(0.33))N — product 29 Present — (Ti_(0.50)Al_(0.50))N (Ti_(0.67)Al_(0.33))N (Ti_(0.50)Al_(0.50))N (Ti_(0.67)Al_(0.33))N (Ti_(0.50)Al_(0.50))N product 30

TABLE 20 First laminated structure Second laminated structure LAYER A1 LAYER B1 LAYER A2 LAYER B2 Average Average Average Average thickness thickness thickness thickness Sample No. (nm) (nm) (nm) (nm) Present 110 110 10 10 product 28 Present 60 60 2 2 product 29 Present 240 240 15 15 product 30

TABLE 21 Coating layer First layer (Substrate Second layer Third layer side) LAYER A1 and LAYER A2 and Fourth layer Fifth layer Lower LAYER B1 LAYER B2 LAYER A1 and LAYER A2 and layer Average Average LAYER B1 LAYER B2 Average Lami- Re- thick- Lami- Re- thick- Lami- Re- Average Lami- Re- Average thick- nated peated ness nated peated ness nated peated thick- nated peated thick- Sample ness struc- times (μm) struc- times (μm) struc- times ness struc- times ness No. (μm) ture (times) TA1 ture (times) TA2 ture (times) (μm) ture (times) (μm) Present 0.5 First 2 0.44 Second 10 0.20 First 4 0.88 Second 30 0.60 product 28 Present 0.5 First 4 0.48 Second 60 0.24 First 6 0.72 Second 160 0.64 product 29 Present — First 2 0.96 Second 20 0.60 First 4 1.92 Second 50 1.50 product 30 Coating layer Eighth layer Sixth layer Seventh layer (Surface LAYER A1 and LAYER A2 and side) LAYER B1 LAYER B2 Upper Average Average layer Lami- Re- thick- Lami- Re- thick- Average Total nated peated ness nated peated ness thick- thick- Sample struc- times (μm) struc- times (μm) ness ness No. ture (times) TB1 ture (times) TB2 (μm) (μm) Present First 6 1.32 Second 50 1.00 0.50 5.44 product 28 Present First 8 0.96 Second 260 1.04 — 4.58 product 29 Present — — — — — — 0.50 5.48 product 30 *“First” and “Second” at the column of “Laminated structure” mean the first laminated structure and the second laminated structure of the Present product with the corresponding number in Table 19 and Table 20.

TABLE 22 First laminated structure Second laminated structure Average thickness Average thickness Substrate side/ Increase in Substrate side/ Increase in Surface side (%) average Surface side (%) average Sample No. (TA1/TB1) × 100 thickness (TA2/TB2) × 100 thickness Present 33 Continuous 20 Continuous product 28 Present 50 Continuous 23 Continuous product 29 Present 50 Stepwise 40 Stepwise product 30

The average thicknesses of the respective layers and the compositions of the respective layers of the obtained samples were measured in the same manner as in Example 1. These results are shown in Tables 19 to 22. In addition, Cutting test 1 and Cutting test 2 which were the same as in Example 1 were carried out by using the obtained samples to evaluate wear resistance and fracture resistance. The evaluation results are shown in Table 23.

Evaluation standard of the processed length until the tool reaches its tool life in Cutting test 1 is as follows.

-   ⊚: 10.5 m or more -   ◯: 10 m or more and less than 10.5 m -   Δ: 9.5 m or more and less than 10 m -   x: Less than 9.5 m

Evaluation standard of the processed length until the tool reaches its tool life in Cutting test 2 is as follows.

-   ⊚: 6 m or more -   ◯: 5.5 m or more and less than 6 m -   Δ: 5 m or more and less than 5.5 m -   x: Less than 5 m

An order of the evaluation is (Excellent) ⊚>◯>Δ> x (Poor). The evaluation of ⊚ or ◯ means that cutting performance is excellent. The results of the obtained total evaluation are shown in Table 23

TABLE 23 Cutting test 1 Cutting test 2 Wear resistance test Fracture resistance test Tool life Tool life Sample No. (m) Evaluation (m) Evaluation Present 10.5 ⊚ 5.9 ◯ product 28 Present 10.2 ◯ 5.8 ◯ product 29 Present 10.4 ◯ 6.2 ⊚ product 30

From the results of Table 23, the results of the wear resistance test of Present products were ⊚ or ◯. From these results, it can be understood that Present products are excellent in wear resistance. In addition, the results of the fracture resistance test of Present products were ⊚ or ◯. From these results, it can be understood that Present products are also excellent in fracture resistance. As can be seen from these results, according to the present invention, it can be understood that wear resistance can be improved without lowering fracture resistance of the coated tool, and tool lives are elongated in spite of having the lower layer and/or the upper layer in Present products.

Utilizability in Industry

According to the present invention, wear resistance can be improved without lowering fracture resistance of the coated tool. According to the present invention, tool life can be elongated than the conventional ones. Accordingly, utilizability in industry of the present invention is high.

Explanation of Reference Numerals

-   1 Substrate -   2 Coating layer -   3 a First laminated structure in which the thickness is thin at the     substrate side -   3 b First laminated structure in which the thickness is thick at the     surface side -   4 a Second laminated structure in which the thickness is thin at the     substrate side -   4 b Second laminated structure in which the thickness is thick at     the surface side -   5 a Layer A1 in which the thickness is thin at the substrate side -   5 b Layer A1 in which the thickness is thick at the surface side -   6 a Layer B1 in which the thickness is thin at the substrate side -   6 b Layer B1 in which the thickness is thick at the surface side -   7 a Layer A2 in which the thickness is thin at the substrate side -   7 b Layer A2 in which the thickness is thick at the surface side -   8 a Layer B2 in which the thickness is thin at the substrate side -   8 b Layer B2 in which the thickness is thick at the surface side 

The invention claimed is:
 1. A coated tool which comprises a substrate, and a coating layer formed onto a surface of the substrate, wherein the coating layer contains a first laminated structure and a second laminated structure, each of the first laminated structure and the second laminated structure are laminated alternately and continuously twice or more, the first laminated structure contains at least two kinds of layers having different compositions, and the two kinds of layers contained in the first laminated structure are alternately laminated twice or more, an average thickness of the layers contained in the first laminated structure is 60 nm or more and 500 nm or less, the second laminated structure contains at least two kinds of layers having different compositions, and the two kinds of layers contained in the second laminated structure are alternately laminated twice or more, an average thickness of the layers contained in the second laminated structure is 2 nm or more and less than 60 nm, the layers contained in the first laminated structure and the second laminated structure contain a compound comprising at least one metal element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Al, Si, Sr, Y, Sn and Bi, and at least one non-metal element selected from the group consisting of carbon, nitrogen, oxygen and boron, and an average thickness of the first laminated structure and an average thickness of the second laminated structure are both stepwisely increased from a substrate side toward a surface side of the coating layer, such that an outermost portion of the first laminated structure and an outermost portion of the second laminated structure have a greater average thickness than remaining portions of the first and second laminated structures; wherein when an average thickness of the first laminated structure nearest to the substrate is given by TA1, and an average thickness of the first laminated structure nearest to the surface of the coating layer is given by TB1, then a ratio of TA1 to TB1 is 5% or more and 50% or less; wherein when an average thickness of the second laminated structure nearest to the substrate is given by TA2, and an average thickness of the second laminated structure nearest to the surface of the coating layer is given by TB2, then a ratio of TA2 to TB2 is 5% or more and 50% or less; wherein when an average thickness of the layers contained in the first laminated structure nearest to the substrate is given by TC1, and an average thickness of the layers contained in the first laminated structure nearest to the surface of the coating layer is given by TD1, then a ratio of TC1 to TD1 is 12% or more and 70% or less; wherein when an average thickness of the layers contained in the second laminated structure nearest to the substrate is given by TC2, and an average thickness of the layers contained in the second laminated structure nearest to the surface of the coating layer is given by TD2, then a ratio of TC2 to TD2 is 5% or more and 70% or less; and wherein a grain size of the first laminated structure is increased with the increase of the average thicknesses of the first laminated structure and the second laminated structure.
 2. The coated tool according to claim 1, wherein an average thickness of the first laminated structure is 0.2 μm or more and 6 μm or less.
 3. The coated tool according to claim 2, wherein: the layers contained in the first laminated structure and the layers contained in the second laminated structure contain a compound comprising: at least two metal elements selected from the group consisting of Ti, Nb, Ta, Cr, W, Al, Si, Sr and Y, and at least one non-metal element selected from the group consisting of carbon, nitrogen, oxygen and boron.
 4. The coated tool according to claim 1, wherein an average thickness of the second laminated structure is 0.02 μm or more and 6 μm or less.
 5. The coated tool according to claim 1, wherein an average thickness of the whole coating layer is 0.22 μm or more and 12 μm or less.
 6. The coated tool according to claim 1, wherein the layers contained in the first laminated structure and the layers contained in the second laminated structure contain a compound comprising at least two metal elements selected from the group consisting of Ti, Nb, Ta, Cr, W, Al, Si, Sr and Y, and at least one non-metal element selected from the group consisting of carbon, nitrogen, oxygen and boron.
 7. The coated tool according to claim 1, wherein: an average thickness of the first laminated structure is 0.2 μm or more and 6 μm or less; and an average thickness of the second laminated structure is 0.02 μm or more and 6 μm or less.
 8. The coated tool according to claim 7, wherein: an average thickness of the whole coating layer is 0.22 μm or more and 12 μm or less.
 9. The coated tool according to claim 1, wherein: an average thickness of a first laminated structure closest to the substrate is thinner than an average thickness of a first laminated structure farther from the substrate; an average thickness of a second laminated structure closest to the substrate is thinner than an average thickness of a second laminated structure farther from the substrate, at least three first laminated structures and at least three second laminated structures are laminated alternately; the total number of layers in each of the first laminated structures increases, with increasing distance from the substrate; the total number of layers in each of the second laminated structures increases, with increasing distance from the substrate; and the total number of layers in any of the first laminated structures is less than the total number of layers in any of the second laminated structures.
 10. A coated tool which comprises a substrate, and a coating layer formed onto a surface of the substrate, wherein the coating layer contains a first laminated structure and a second laminated structure, each of the first laminated structure and the second laminated structure are laminated alternately and continuously twice or more, the first laminated structure contains at least two kinds of layers having different compositions, and the two kinds of the layers contained in the first laminated structure are alternately laminated twice or more, an average thickness of the layers contained in the first laminated structure is 60 nm or more and 500 nm or less, the second laminated structure contains at least two kinds of layers having different compositions, and the two kinds of the layers contained in the second laminated structure are alternately laminated twice or more, an average thickness of the layers contained in the second laminated structure is 2 nm or more and less than 60 nm, the layers contained in the first laminated structure and the second laminated structure contain a compound comprising at least one metal element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Al, Si, Sr, Y, Sn and Bi, and at least one nonmetal element selected from the group consisting of carbon, nitrogen, oxygen and boron, an average thickness of a first laminated structure closest to the substrate is thinner than an average thickness of a first laminated structure farther from the substrate; an average thickness of a second laminated structure closest to the substrate is thinner than an average thickness of a second laminated structure farther from the substrate; the average thickness of the first laminated structure and the average thickness of the second laminated structure are both stepwisely increased from a substrate side toward a surface side of the coating layer, such that an outermost portion of the first laminated structure and an outermost portion of the second laminated structure have a greater average thickness than remaining portions of the first and second laminated structures; wherein when an average thickness of the first laminated structure nearest to the substrate is given by TA1, and an average thickness of the first laminated structure nearest to the surface of the coating layer is given by TB1, then a ratio of TA1 to TB1 is 5% or more and 50% or less; wherein when an average thickness of the second laminated structure nearest to the substrate is given by TA2, and an average thickness of the second laminated structure nearest to the surface of the coating layer is given by TB2, then a ratio of TA2 to TB2 is 5% or more and 50% or less; wherein when an average thickness of the layers contained in the first laminated structure nearest to the substrate is given by TC1, and an average thickness of the layers contained in the first laminated structure nearest to the surface of the coating layer is given by TD1, then a ratio of TC1 to TD1 is 12% or more and 70% or less; wherein when an average thickness of the layers contained in the second laminated structure nearest to the substrate is given by TC2, and an average thickness of the layers contained in the second laminated structure nearest to the surface of the coating layer is given by TD2, then a ratio of TC2 to TD2 is 5% or more and 70% or less; and wherein a grain size of the first laminated structure is increased with the increase of the average thicknesses of the first laminated structure and the second laminated structure.
 11. The coated tool according to claim 10, wherein: at least three first laminated structures and at least three second laminated structures are laminated alternately; the total number of layers in each of the first laminated structures increases, with increasing distance from the substrate; and the total number of layers in each of the second laminated structures increases, with increasing distance from the substrate.
 12. The coated tool according to claim 11, wherein: the total number of layers in any of the first laminated structures is less than the total number of layers in any of the second laminated structures. 